Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 010944
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
243 AM PDT TUE SEP  1 2015

.SYNOPSIS...A COLD FRONT ALONG THE CENTRAL WASHINGTON COAST WILL
SLOWLY MOVE SOUTHWARD INTO SOUTHWEST WASHINGTON AND EXTREME NORTHWEST
OREGON TODAY...AND INTO THE REMAINDER OF NORTHWEST OREGON TONIGHT FOR
A LITTLE LIGHT RAIN OR SHOWERS. THE SOUTHERN PART OF THE ASSOCIATED
TRAILING UPPER LOW WILL SLOWLY EXTEND INTO SOUTHWEST WASHINGTON AND
NORTHWEST OREGON WEDNESDAY FOR MORE SHOWERS...AND LINGER OVER THE
PACIFIC NORTHWEST THURSDAY. ENERGY ON THE WEST OR BACK SIDE OF THE
UPPER LOW WILL DROP DOWN ALONG THE COAST THURSDAY NIGHT THEN SWING
INLAND MAINLY SOUTH OF OUR FORECAST AREA FRIDAY. HOWEVER...THE COLDER
AIR ALOFT WILL BE MORE OVER OUR AREA FRIDAY FOR A GREATER CHANCE OF
AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS. THE LOW WILL MOVE
OFF TO THE EAST THIS WEEKEND FOR IMPROVING WEATHER...THOUGH ANOTHER
SYSTEM IS POSSIBLE EARLY NEXT WEEK.
&&

.SHORT TERM...SATELLITE IMAGERY AND NATIONAL WEATHER SERVICE DOPPLER
RADAR SHOW A FRONT ALONG THE CENTRAL WASHINGTON COAST EARLY THIS
MORNING. THE UPPER CLOUDS WITH THIS FRONT HAVE SHEARED OFF TO THE
EAST OF THE CASCADES. THE LOWER LEVEL CLOUDS ARE SLOWLY MOVING
SOUTHWARD. THE MODELS SHOW IT SLOWLY MOVING INTO SOUTHWEST WASHINGTON
AND EXTREME NORTHWEST OREGON TODAY...THEN ACROSS THE REMAINDER OF
NORTHWEST OREGON TONIGHT. INFRARED SATELLITE IMAGERY SHOWS A JET
STREAK/SHORT WAVE OUT AROUND 45N/135W THAT THE MODELS MOVE THROUGH
THE PACIFIC NORTHWEST THIS AFTERNOON AND EVENING. THIS APPEARS TO BE
THE FEATURE THAT WILL KEEP THE FRONT SOMEWHAT ACTIVE AS IT MOVES INTO
OUR FORECAST AREA. PRECIPITATION WILL NOT BE A LOT WITH THIS
FRONT...PERHAPS A QUARTER INCH ON THE NORTH COAST AND IN THE COASTAL
MOUNTAINS...UP TO A TENTH IN THE NORTH VALLEY...AND ONE OR TWO TENTHS
IN THE CASCADES...WITH LESSER AMOUNTS IN THE SOUTH.

ON WEDNESDAY THE SOUTHERN PART OF THE ASSOCIATED UPPER LOW EXTENDS
SOUTHWARD INTO OUR FORECAST AREA. THIS SHOULD PRODUCE SOME DECENT
SHOWERS ESPECIALLY DURING THE FIRST HALF OR SO OF THE DAY AS A DECENT
SHORT WAVE MOVES THROUGH. THERE MAY BE ENOUGH COOLING ALOFT FOR A
SLIGHT CHANCE OF THUNDER AS WELL...AND MODEL LIFTED INDICES SUPPORT
THIS IDEA.

THE UPPER TROUGH LINGERS AND SAGS A LITTLE FARTHER SOUTH ON THURSDAY
FOR SOME MORE SHOWERS...AND A ANOTHER SHORT WAVE MOVES THROUGH AS
WELL. THERE MAY BE ANOTHER CHANCE OF THUNDER AS WELL IN THE AFTERNOON
AND EVENING.

TEMPS WILL STAY BELOW NORMAL THROUGH THE PERIOD...HOVERING ON ONE
SIDE OR THE OTHER OF 70 IN THE NORTH...AND A FEW DEGREES WARMER NEAR
EUGENE.

SNOW LEVELS WILL BE LOWERING TO POSSIBLY AS LOW AS 6000 TO 7000 FEET
AROUND MOUNT HOOD NORTHWARD...THE LOWEST WE HAVE SEEN SINCE SPRING.
TOLLESON

CLIMATE FACTOID...GIVEN THE HIGH AND LOW TEMPERATURES OBSERVED SO FAR
TODAY AND NO DRASTIC TEMPERATURE CHANGES ARE EXPECTED IN THE NEXT
COUPLE OF HOURS...2015 WILL GO DOWN AS THE WARMEST METEOROLOGICAL
SUMMER...JUNE...JULY AND AUGUST...ON RECORD FOR PORTLAND...SALEM AND
EUGENE. RECORDS GO BACK APPROXIMATELY 120 YEARS FOR EUGENE AND
SALEM...AND 75 YEARS FOR PORTLAND. WILL PUT A GRAPHIC COMPARING THIS
YEAR TO THE PREVIOUS RECORDS ON OUR SOCIAL MEDIA SITES HOPEFULLY
BEFORE 10 PM. LINKS TO OUR SOCIAL MEDIA SITES CAN BE REACHED AT THE
BOTTOM OF THE AFD OR IN THE UPPER RIGHT HAND CORNER OF OUR HOMEPAGE.
/NEUMAN

.LONG TERM...THURSDAY NIGHT THROUGH MONDAY. THE MODELS ARE COMING
TOGETHER WITH THE UPPER LOW DROPPING SOUTHWARD ON THURSDAY NIGHT AND
FRIDAY. THE INITIAL MAIN ENERGY DROPS SOUTH ALONG THE COAST AND THEN
SWINGS INLAND MAINLY TO OUR SOUTH. BUT THEN WE WILL BE UNDER A
BROADER PORTION OF THE COLD POOL ALOFT FOR FRIDAY AFTERNOON AND
EVENING...AND EXPECT SOME DIURNAL SHOWERS AND POSSIBLY A FEW
THUNDERSTORMS TO DEVELOP AROUND THE AREA. THE UPPER LOW MOVES OFF TO
THE EAST OVER THE WEEKEND THAT SHOULD BRING SOME IMPROVING WEATHER TO
THE AREA. THE MODELS SUGGEST THE NEXT SYSTEM COULD ARRIVE SOMETIME
EARLY NEXT WEEK. TOLLESON
&&

.AVIATION...CONTINUED VFR CONDITIONS ACROSS THE REGION AT THIS HOUR
AS MID LEVEL CLOUDS APPEAR TO HAVE KEPT A DECENT TEMPERATURE/DEW
POINT SPREAD AND THUS PREVENT LOW STRATUS FROM FORMING AT THE COAST.
STILL LOOKING LIKE POST COLD FRONTAL ONSHORE WIND WILL BRING AN IFR
DECK AROUND 18-23Z TODAY TO KAST AND A COUPLE HOURS LATER TO KONP.
INLAND SITES SHOULD NOT DROP LOWER THAN A HIGH END MVFR AT WORST AND
PROBABLY REMAIN VFR WITH CIGS AROUND 035.

KPDX AND APPROACHES...VFR ALTHOUGH CIGS CLOUDS LOWER TO 035 AS A WEAK
COLD FRONT CROSSES THE FIELD 20-23Z. /JBONK
&&

.MARINE...WINDS ARE RUNNING 10 TO 15 KT ACROSS THE WATERS PER
RAPIDSCAT AND ASCAT WIND PASSES. HAVE ANTICIPATED A BIT OF A COASTAL
JET DEVELOPING THIS MORNING WITH THE PRIMARY FOCUS ALONG THE NRN
OREGON AND SRN WA COAST. WINDS AT CLATSOP SPIT SENSOR ARE RUNNING
AROUND 15 KT AND HAVE OVER ACHIEVED MOST MODELS THUS FAR TONIGHT. THE
HRRR SEEMS TO HAVE A GOOD HANDLE ON IT AND WILL FOLLOW IT`S WINDS AND
MINIMAL COASTAL JET FOR THE NEXT SEVERAL HOURS. AS SUCH...HAVE ISSUED
A SMALL CRAFT ADVISORY FOR WINDS COVERING THE NORTHERN INNER WATERS.
EXPECT WINDS WILL GUST TO AROUND 25 KT.

THOSE WINDS MAY EXACERBATE THE ALREADY SOMEWHAT STEEP SEAS AND BRING
CONDITIONS LONG THE MOUTH OF THE COLUMBIA UP TO 10 FT. WILL KEEP AN
EYE ON IT AS ONLY HAVE MEDIUM CONFIDENCE. OTHERWISE...SEAS WILL STAY
IN THE 7 TO 9 FT RANGE WITH PERIODS 11 TO 13 SECONDS THROUGH MID-DAY
TOMORROW.

A SURFACE LOW OVER THE GULF OF ALASKA...JUST OFFSHORE OF YAKUTAT IS
GENERATING A NORTHERLY FETCH THAT WILL BRING A BRIEF PERIOD OF 10 FT
SWELL TO THE OUTER OREGON WATERS TUESDAY NIGHT AND EARLY WEDNESDAY.

RECENT MODEL RUNS HAVE BACKED OFF ON THE UPPER RIDGE BUILDING OVER
THE REGION HEADING INTO THE WEEKEND. STILL EXPECTING NORTHERLY WINDS,
BUT THE SURFACE THERMAL LOW OVER THE NRN CA AND SRN OR COAST WILL BE
WEAKER AND MAY NOT EVEN PUSH VERY FAR OVER OREGON. HAVE KEPT THE
NORTHERLIES FOR NOW. /JBONK
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS FROM 7 AM THIS MORNING TO 4 PM
     PDT THIS AFTERNOON FOR COASTAL WATERS FROM CAPE SHOALWATER
     WA TO CASCADE HEAD OR OUT 10 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 9 AM PDT
     THIS MORNING.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR FROM 5 PM
     THIS AFTERNOON TO 10 PM PDT THIS EVENING.

&&

$$

INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/NWSPORTLAND
WWW.TWITTER.COM/NWSPORTLAND

THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON
FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS
COMMONLY REFERRED TO AS THE FORECAST AREA.


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